I want to buy DDNS

hi.I want to buy DynDNS Domain, , but I need to connect to it 15 modems, which are located throughout Ukraine, so that I can access them. Tell me please, is it possible that I need it and how much will it cost?

I have 15 Robustel modems, they all support DynDNS, but they are located all over the country, and in most places there is no static address, but I need to have access to them. How much will this service cost?